I understand how you feel. My Mom died this year, my only child died last year.
Symbolic dates are always difficult. Birthdays, anniversaries, holidays. Although you doubt it now, it will get easier. You won't miss them less, you will just accept it more.
I will pass on a story to you. You may find some comfort there.
My Mom always had a more-than-healthy fear of death. Any aspect of death and dying. Couldn't touch our dead pets we had as children. Terrified of her own death.
She had a chronic, progressive lung disease. On oxygen for the last several years of her life.Facing her own death never got any easier for her.
In July she got an upper respirator infection. They gave her antibiotics, but she wound up in ICU on a respirator anyway. This was not unusual for her, her lungs were so weak she always needed some mechanical help before she bounced back. This time was different. There wasn't any improvement over time. She was a good patient - she knew the purpose of the machine and it didn't scare her. Her sedation was minimal. She was lucid, and although she couldn't talk, she could communicate by my going through the alphabet and her signalling when I got to the right letter. We spelled out our conversations in this way.
The doctors finally determined that she had zero lung function left. The damage from the last infection was devastating. They suggested terminating life support.
An agonizing decision, to say the least. Finally she told me "I'm not going to make it, take me home". They wouldn't let me take her home, but I started the preparations for her transition. She was still terrified, but didn't want to live on the machine. I set the date. Made arrangements for her friends to come and see her for the last time. She was Catholic, but had very little faith in any sort of afterlife. Not a metaphysical bone in her body. Truly believed that when you die everything about you is gone. Going home that night, leaving this terrified woman, knowing that I was about to sign her execution papers, was one of the hardest things I had ever done.
When I arrived early the next morning, there was a totally different energy radiating from her. Calm. At peace. Unafraid. When I asked her about it, she spelled out "Your son". It seems that my son Michael, who had died the year before, had come to her during the night. She wouldn't tell be about the conversation, other than the fact that she wasn't afraid any more and ready to go. In fact, she was anxious to go. She refused any meds the nurses tried to bring her. She wanted that machine off now! I told her she had to wait until her friends came, as they wanted to see her. I had told them to arrive between 9am and noon. She had last rites as that was a part of her faith. I am not Catholic but it was beautiful. References to our body being nothing more than a tent for our soul and although it was time to break camp, the soul lives on. Her friends came. They were teary and sad. She was upbeat and joking. The machine was removed at noon. She died 2.5 hours later. I wish I could tell you she passed on some great words of wisdom or even a couple of I love yous during her dying process. I can't. She was peaceful. I held her hand.
What I can pass on is that no matter what your belief system calls it, something about us truly is eternal. My son crossing the dimension to reach out to his dying grandmother is proof enough for me. It shows that those who have passed do see what is happening in this plane. So, in that respect, your Dad truly is aware of the improvements you have made in your life. I am sure he is proud that you are making yourself the best possible you that you can be.